The present invention relates to an exhaust arrangement for a multi-cylinder internal combustion engine of a vehicle.
For the purpose of effectively conducting emission control in a vehicle, there is a demand to provide an exhaust arrangement in which a catalyst is disposed near a combustion chamber of an engine in order to early activate the catalyst at a low temperature upon engine starting operation. In a front-engine front-wheel drive vehicle (FF vehicle) including an engine disposed on the right or left side of an engine room, a catalyst is arranged at substantially a central part of the vehicle and along a fore-and-aft direction of the vehicle. Accordingly, in the FF vehicle, an exhaust pipe connecting the engine and the catalyst has a generally crank shape.
On the other hand, there is known an exhaust manifold which includes a branch portion constituted of a plurality of branch pipes corresponding to engine cylinders. The branch pipes are merged into an exhaust collector on the downstream side. An exhaust pipe connects the exhaust collector with a catalyst disposed downstream of the exhaust collector. The exhaust pipe has a two-part split construction in which two separate exhaust passages extend between the exhaust collector and the catalyst. There is a demand for elongating the two exhaust passages in order to reduce the number of engine revolution required for avoiding the exhaust interference among the engine cylinders.
Japanese Utility Model Application First Publication No. 52-164602 discloses an exhaust arrangement in which two separate exhaust passages are provided. FIGS. 10 and 11 show such an exhaust arrangement as described in this related art. As shown in FIG. 10, exhaust manifold 40 including four branch pipes 41A-41D corresponding to engine cylinders of engine 39, and exhaust collector 42 connected with downstream portions of branch pipes 41A-41D. Exhaust collector 42 is coupled to first and second exhaust pipes 48 and 49 which are joined together at combined portion 50. As illustrated in FIG. 11, partition wall 43 is disposed within exhaust collector 42 and divides an exhaust path within exhaust collector 42 into first and second exhaust passages 44 and 45. Branch pipes 41A and 41D are communicated with first exhaust passage 44, and branch pipes 41B and 41C are communicated with second exhaust passage 45. Partition wall 43 has notch 46 in which oxygen sensor 47 is arranged to face an interior of each of first and second exhaust passages 44 and 45. Oxygen sensor 47 detects an oxygen content in exhaust flowing in each of first and second exhaust passages 44 and 45. First and second exhaust passages 44 and 45 are communicated with exhaust passages within first and second exhaust pipes 48 and 49. The exhaust passages within first and second exhaust passages 44 and 45 are merged into a single exhaust passage via combined portion 50.
In the related art described above, exhaust collector 42 as well as partition 43 are curved. Exhaust collector 42 has an outside curving portion with a longer curve length and an inside curving portion with a shorter curve length about a center of curvature. Partition wall 43 is similarly curved and has opposed surfaces perpendicular to a direction of a row of the engine cylinders. When viewed in FIG. 11, partition wall 43 is perpendicular to a sheet plane of FIG. 11. Similar to exhaust collector 42, the opposed surfaces of partition wall 43 respectively form outside and inside curving portions with respect to a center of curvature. Oxygen sensor 47 is disposed in notch 46 formed in partition 43 so as to be exposed an interior of each of first and second exhaust passages 44 and 45. The exhaust flowing from the engine cylinders into first and second exhaust passages 44 and 45 gathers at the outside curving portion of exhaust collector 42 and the outside curving portion of partition wall 43. Namely, the exhaust flowing in each of first and second exhaust passages 44 and 45 is concentrated at the respective outside curving portions of exhaust collector 42 and partition wall 43. Therefore, the exhaust flowing in first exhaust passage 44 cannot be efficiently directed toward oxygen sensor 47 as compared with the exhaust flowing in second exhaust passage 45. This leads to inaccurate detection of the oxygen content in the exhaust flowing in first and second exhaust passages 44 and 45.
It would be therefore desirable to provide an exhaust arrangement for an internal combustion engine, in which both emission control and output performance of the engine can be improved.
In one aspect of the present invention, there is provided an exhaust arrangement for a multi-cylinder internal combustion engine of a vehicle, the engine including a row of cylinders, the exhaust arrangement comprising:
an exhaust manifold including a branch portion including a plurality of branch pipes corresponding to the cylinders;
a catalyst disposed downstream of the exhaust manifold;
an exhaust pipe connecting the exhaust manifold to the catalyst, the exhaust pipe defining an exhaust path;
a bend formed in the exhaust pipe, the bend including a plane which divides an interior of the bend into equal halves;
a partition dividing the exhaust path into first and second exhaust passages coextending in a longitudinal direction of the exhaust pipe, the partition extending in the bend in alignment with the plane; and
an oxygen sensor disposed at the bend of the exhaust pipe in alignment with the partition, the oxygen sensor projecting into both of the first and second exhaust passages through a periphery of the partition.
In a further aspect of the present invention, there is provided an exhaust arrangement for a multi-cylinder internal combustion engine of a vehicle, the engine including a row of cylinders, the exhaust arrangement comprising:
an exhaust manifold including a branch portion including a plurality of branch pipes corresponding to the cylinders;
a catalyst disposed downstream of the exhaust manifold;
passage means for defining an exhaust path having a length extending from the exhaust manifold to the catalyst;
bending means for bending the exhaust path to provide the exhaust path with a curve;
partition means for dividing the exhaust path into first and second exhaust passages coextending along the length of the exhaust path, the partition means equalizing the first and second exhaust passages at the curve; and
a sensor projecting into both of the first and second exhaust passages at the curve through the partition means.
In a still further aspect of the present invention, there is provided an exhaust arrangement for a multi-cylinder internal combustion engine of a vehicle, the engine including a row of cylinders, the exhaust arrangement comprising:
an exhaust manifold including a branch portion including a plurality of branch pipes corresponding to the cylinders;
a catalyst disposed downstream of the exhaust manifold;
an exhaust pipe connecting the exhaust manifold to the catalyst, the exhaust pipe defining an exhaust path, the exhaust pipe having a longitudinal axis;
a bend formed in the exhaust pipe, the bend including a plane in which the longitudinal axis of the exhaust pipe lies, the bend including an inner curving periphery and an outer curving periphery extending longer than the inner curving periphery;
a partition dividing the exhaust path into first and second exhaust passages, the partition extending in the bend in alignment with the plane; and
an oxygen sensor disposed at the outer curving periphery of the bend in alignment with the partition, the oxygen sensor projecting into both of the first and second exhaust passages through a periphery of the partition.